Waiting for the Discovery of B^0_d -> K^0 \bar K^0

Abstract

The CP asymmetries of the decay B_d^0 -> K^0 \bar K^0, which originates from \bar b -> \bar d s \bar s flavour-changing neutral-current processes, and its CP-averaged branching ratio BR(B_d -> K^0 \bar K^0) offer interesting avenues to explore flavour physics. We show that we may characterize this channel, within the Standard Model, in a theoretically clean manner through a surface in observable space. In order to extract the relevant information from BR(B_d -> K^0 \bar K^0), further information is required, which is provided by the B -> pi pi system and the SU(3) flavour symmetry, where we include the leading factorizable SU(3)-breaking corrections and discuss how experimental insights into non-factorizable effects can be obtained. We point out that the Standard Model implies a lower bound for BR(B_d -> K^0 \bar K^0), which is very close to its current experimental upper bound, thereby suggesting that this decay should soon be observed. Moreover, we explore the implications for ``colour suppression'' in the B -> pi pi system, and convert the data for these modes into a peculiar Standard-Model pattern for the CP-violating B_d^0 -> K^0 \bar K^0 observables.